1. Field of the Invention
The present invention relates to a frame structure for supporting a light emitting diode, and in particular to a frame structure for supporting a surface mount device (SMD) light emitting diode used as a side light source.
2. Description of Related Art
Light emitting diode (LED) is a semiconductor device that emits light when electrically biased in the forward direction. When voltage is applied to the semiconductor device such as gallium phosphide (GaP) or gallium arsenide (GaAs), charge-carriers (electrons and electron holes) flow into the junction from electrodes because of voltage. When electrons meet electron holes, the semiconductor device releases energy in the form of a photon unlike incandescent and discharging light sources. Because the LED is an electroluminescent device, life expectancy of the LED is up to 100,000 hours. Besides, the LED is compact, energy-saving, fit to mass production and clean so the LED is widely used, such as traffic lights and signals, backlight for electronic appliance, car's break light and lighting apparatus etc.
Referring to FIGS. 1 and 2, they show a frame structure for a surface mount device (SMD) LED used as a side light source. The frame structure is used to support a LED die so that a LED structure is formed and used as side-type backlight module for cellular phones or personal digital assistants (PDAs). The frame structure includes a plastic housing 10a and two metallic support frames 20a with different electrical polarities. The plastic housing 10a includes a receiving space 11a, and the two metallic support frames 20a are positioned within the plastic housing 10a. A LED die 30a is positioned at one of the two metallic support frames 20a, and the LED die 30a and the two metallic support frames 20a are electrically connected by conductive wires (not shown). The LED die 30a is packaged by an epoxy layer or a silicon layer and a packaging layer 40a, and the packaging layer 40a includes a variety of fluorescent powder. Besides, positive and negative polarities of electrical current are respectively applied to the two metallic support frames 20a so that the LED die 30a emits light.
However, electronic appliances need to be slim, compact and light-weighted to meet users' requirement. Thus, the frame structure for a surface mount device (SNM) LED should be smaller and thinner. If the plastic housing 10a is too smaller, then thickness d is thin so that the LED die 30a emits light through the plastic housing 10a. That is what is so called “light leakage”. Besides, the two metallic support frames 20a are mostly enclosed by the plastic housing 10a so it is not easy for the LED die 30a to dissipate heat. Life expectancy of the LED die 30a is significantly shortened because of high temperature.
Thus, there is a need for a frame structure for supporting a light emitting diode used as a side light source.